1. Field of the Invention
This invention relates to a paint booth with a purifier for removing paint mist permeating the air in a coating chamber.
2. Description of the Related Art
In performing a coating operation by means of a paint sprayer such as a device comprising spray nozzles in a coating chamber, a paint booth with a purifier is used in order to prevent the working environment in the coating chamber from being degraded or to prevent paint mist from being discharged to the outside. In a paint booth of the Venturi booth type disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-273292 (Patent Document 1), air containing paint mist is drawn into an eddy chamber by an exhaust fan, and the paint mist is separated from the airflow by means of centrifugal force in the eddy chamber. Further, moist air delivered from the eddy chamber is discharged through an exhaust port after being dehydrated by an eliminator. In a paint booth of the water booth type disclosed in Japanese Patent No. 3704084 (Patent Document 2), on the other hand, a water curtain is formed by pouring water drawn up by a pump in the form of a film along a water flow plate. The paint mist is washed away when it contacts this water curtain.
In either of the paint booths disclosed in Patent Documents 1 and 2, collected paint mist is deposited together with water in a water tank and condenses, thereby forming paint sludge (paint residue) in the water tank. This paint sludge accumulates in the water tank, floating on the water surface or settling in the water tank. Since conventional paint booths do not comprise a mechanism for purifying water in the water tank, an operator or operators must periodically manually remove the paint sludge. However, the periodic cleaning cannot purify contaminated water unless the water is changed. Accordingly, the paint sludge gradually accumulates in the water tank and solidifies at the bottom of the water tank or near the water surface, and therefore, cannot be easily removed and causes contamination. In the water booth type (Patent Document 2), the paint mist contacts only one surface of the water curtain, so that the surface area that allows collection of the paint mist is limited. Thus, the capacity to collect the paint mist is small.
In order to solve these problems, the inventors hereof have developed such a paint booth with a purifier as that shown in International Publication No. W02010/131564A1 (Patent Document 3). Although the paint booth of Patent Document 3 is more compact than the paint booths of Patent Documents 1 and 2, it can efficiently collect the paint mist.
In order to improve the working environment in a coating chamber, airflow from a booth opening toward an exhaust chamber must be produced at a certain speed or higher. To this end, Article 16 of the current Ordinance on the Prevention of Organic Solvent Poisoning in Japan states that the minimum air speed at the booth opening should be 0.4 m/s or more. If air in the coating chamber is discharged by means of an exhaust fan, however, the water surface of a water tank of a purifier is undulated by air flowing near the water surface, so that paint sludge in water cannot easily gather near the water surface. Thus, it is difficult to efficiently remove the paint sludge in the water tank by means of a conveyor of the purifier.